THE AMIDO-ACIDS. 85 



On oxidation with mercuric oxide kreatin gives rise to the forma- 

 tion of the oxalate of methyl-guanidin or methyl-uramin, which in 

 turn results from guanidin, and this from guanin. 



2C 4 H 9 N 3 2 + 5O = (C 2 H 7 N 3 ) 2 .C 2 H 2 4 + 2CO 2 + H 2 O 

 Kreatin. Methyi-guanidiu 



oxalate. 



On decomposition with baryta-water kreatin yields urea, methyl- 

 glycocoll, and a small amount of hydantoic acid. Kreatinin is 

 similarly transformed into methyl-hydantoin, which is then likewise 

 decomposed into urea and methyl-glycocoll, thus demonstrating 

 the close relationship which exists between the kreatins and the 

 ureids. 



X NH 2 CH 2 NH.CH 3 



NH = C/ +H 2 0= | + CO(NH 2 ) 2 



X N(CH 8 ) CH 2 COOH COOH Urea. 



Kreatiii. Methyl-glycocoll. 



N H - CO /NH - CO 



NH = C< | + H 2 = NH 3 + C0< | 



\N(CH 3 ) CH 2 X N(CH 3 ) CH 2 



Kreatinin. Methyl-hydantoin. 



Kreatin and kreatinin are homologous with lysatin and lysatinin, 

 which, as has been seen, result from albuminous material when this 

 is decomposed with boiling mineral acids. While kreatin, however, 

 contains but four atoms of carbon, lysatin contains six, and is 

 represented by the formula C 6 H 13 N 3 O 2 . Like kreatin and kreatinin, 

 lysatin and lysatinin yield urea on hydrolytic decomposition. 



The individual representatives of the group will be considered 

 later. 



THE AMIDO-ACIDS. 



The amido-acids represent one of the most important groups of 

 chemical substances which are found in the animal and the vegetable 

 world. They are intimately concerned in the construction of the 

 albuminous molecule, and are accordingly always found among the 

 decomposition-products of all albumins. Some of them belong to 

 the so-called diamido-acids, while others are mono-amido-acids. 

 With the latter AVC shall deal more exclusively at this place. They 

 are generally of the character of a fatty acid or of an aromatic acid, 

 in which one hydrogen atom of the group CH 3 or C 6 H 5 has been 

 replaced by the amido-radicle NH 2 . Acetic acid thus gives rise to 

 mono-amido-acetic acid, and benzoic acid to mono-amido-benzoic 

 acid, etc., as shown by the formulae : 



CH 3 .COOH, acetic acid. 

 CH 2 (NH 2 ).COOH, mono-amido-acetic acid. 

 C 6 H 5 .COOH, benzoic acid. 

 C 6 H 4 .(NH 2 ).COOH, mono-amidobenzoic acid. 



